A main wing of an aircraft may be used as a fuel tank capable of storing fuel. A fuel tank that forms an integral part of the main wing, the wing structure having a liquid-tight structure that prevents fuel leakage, is referred to as an integral tank. Composite materials such as carbon-fiber-reinforced plastic (CFRP) tend to be used for integral tanks with the goal of reducing weight. In CFRP, carbon fibers are used as a reinforcing material, and a synthetic resin is used as a matrix.
Patent Document 1 discloses an invention of a three-dimensional fiber-reinforced resin composite material in which selvage threads are formed from an electrically conductive material having a higher level of electrical conductivity than in-plane directional threads in order to impart the fiber-reinforced resin composite material with electrical conductivity without reducing productivity. Patent Document 2 discloses an invention of a prepreg and a carbon-fiber-reinforced composite material in which electrically conductive particles or fibers are included in order to provide both superior impact resistance and electrical conductivity. Patent Document 3 discloses an invention of an improved composite material that contains electrically conductive particles dispersed within a polymer resin in order to impart electrical conductivity while substantially or entirely avoiding increased weight over a standard composite material.